1. Field of the Invention
The present invention relates to a temperature control unit, and a temperature control apparatus using it, for resin-coated sand used in a shell molding process for sand-casting, raw molding sand used in an organic material cold-self-hardening-nature process or a cold box process, etc., in a flowing state (the raw molding sand or resin-coated sand used in shell molding process are collectively referred to hereinafter as xe2x80x9cpowderxe2x80x9d).
2. Description of the Related Art
As an example, resin-coated sand is molding sand coated with bonding material such as thermosetting phenol resin, which is baked after being charged into a heated mold to be formed in a mold. Furthermore, for example, although mixed sand used in a cold-box process has the property of being susceptible to the temperature at molding, the raw molding sand with which the sintering material-coated sand is made is used with little temperature control.
However, resin-coated sand is apt to cause a reduction in the productivity of a mold due to the extension of baking time, the occurrence of mold breakage, etc. in winter, while the sintering material-coated sand, for a cold-box process, made of ambient temperature raw molding sand without temperature control becomes hard slowly in winter and the time the sintering material-coated sand can be able to be used is short in summer, thereby interfering with the molding.
Up to now, it has been considered that a heat exchanging process (heating or cooling) by a temperature control apparatus such as a heating apparatus for heating powder while keeping it in a fluidizing state with blown up warm air (Japanese Examined Utility Model Publication No.59-35127, Japanese Unexamined Patent Publication No.55-109541), a heating and cooling apparatus having tubes allowing a heat carrier to flow within a temperature control bath (Japanese Examined Utility Model Publication No.59-35318), and a heating apparatus for heating powder while blowing warm air down (Japanese Unexamined Patent Publication No.59-191540), etc., serves a useful function for such powder which is susceptible to ambient temperature.
However, those temperature control apparatuses have not become widespread because it is difficult to reduce the installation cost or the installation space as they are in general large, for processing a large quantity of powder, and require appurtenant work for conveying the powder to the place where the powder is used after the heat exchanging process. In such circumstance, it has been desired to develop a small temperature control apparatus capable of being installed at each service place such as a mixer for manufacturing sintering material-coated sand used for a cold-box process or a molding machine for shaping a mold.
It is therefore an object of the present invention to provide a temperature control unit which can be used to modify various existing or newly installed hoppers, as a related apparatus of a mold shaping machine or mixer, including, for example, a powder receiving reservoir (called xe2x80x9cpowder reservoirxe2x80x9d hereinafter) shaped like a cone, cylinder tube, rectangular tube, or diameter-decreased tube, to a temperature control apparatus which has a heat exchanging ability corresponding to the amount of powder to be processed, is able to prevent the occurrence of dust from the powder and the exfoliation of the resin film of the powder, and is smaller than conventional temperature control apparatuses. It is another object of the present invention to provide a temperature control unit which is able to allow a satisfactory flow, in the heat exchange portion, of the powder conveyed into the reserving portion of a powder reservoir irrespective of the weight of the powder, and the supply of the powder from the reserving portion to the heat exchange portion without any trouble, and thus allow the continuous processing for the powder. It is further object of the present invention to provide a temperature control apparatus capable of switching between the heating and cooling of powder.
The inventor et al found that their predetermined goal can be accomplished by using a temperature control unit basically comprising a particular heat exchanger and a particular gas distribution tube assembly for making powder flow, after due consideration mainly of downsizing a temperature control apparatus, and have made further study based on this finding to accomplish the present invention.
The present invention relates to:
(1) a temperature control unit for raw molding sand or resin-coated sand for a shell mold, comprising a heat exchanger A consisting of a spiral hollow tube (called xe2x80x9cspiral heat exchanger Axe2x80x9d hereinafter) allowing a heat carrier (xe2x80x9cHeat carrierxe2x80x9d means a heat carrier used for heating and a heat carrier used for cooling in this specification.) to flow, and a gas distribution tube assembly for making powder flow for supplying gas to cause the flow of raw molding sand or resin-coated sand for a shell mold (powder);
(2) preferably a temperature control unit of (1) further comprising a buffer C for preventing the influence of the weight of raw molding sand or resin-coated sand for a shell mold (powder) disposed above the spiral heat exchanger A and/or under the gas distribution tube assembly for making powder flow B; or
(3) a temperature control unit of (1) or (2), wherein the lower part of the gas distribution tube assembly B for making powder flow has a plurality of gas diffusing holes.
The present invention further relates to:
(4) a temperature control apparatus for raw molding sand or resin-coated sand for a shell mold (powder) comprising a reservoir for raw molding sand or resin-coated sand (powder) in which the temperature control unit of anyone of (1) to (3) is installed;
(5) preferably a temperature control apparatus of (4) further comprising a pair of level controller disposed on the reserving portion 1 at the upper part of the reservoir for raw molding sand or resin-coated sand (powder); or
(6) a temperature control apparatus of (4) or (5) capable of switching between the heating or cooling of raw molding sand or resin-coated sand for a shell mold.